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      The Unreliability of 14C Dates Obtained from Buried Sandy Podzols

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          Abstract

          A test for the reliability of 14C dating of soil was made at two sites with buried, autochthonous, and in parts, allochthonous sandy podzols, dated either litho- and pedostratigraphically or palynologically. The differences between the age ranges obtained and the apparent mean residence times (AMRT) calculated from the 14C content of alkaline extracts from fossil soil layers and horizons lean in organic matter exceed 10,000 years, corresponding to a maximum contamination with recent carbon of up to 50 %. The use of correction factors for the apparent mean residence times of podzols is not valid, not even for climate zones, because these values have a broad scatter for the same profile.

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          Radiocarbon dating of soils, a review

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            Natural14C age/depth gradient in a buried soil

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              Unreliability of 14C Dates from Organic Matter of Soils

              Contamination by recent carbon and the turnover of organic matter make dating of ancient soils difficult. In order to isolate the oldest organic fraction of sediments, two main extraction methods were previously proposed: 1) alkaline solubilization of humus that separates humins, humic acids, and fulvic acids, and 2) successive hydrolyses that solubilize increasingly resisting products. Both preparation methods were tested on the same actual or fossil soils of different pedologic types from five geologic profiles on which other chronologic data are available. Analytic results show that 14 C ages obtained from alkaline extraction products differ according to the duration of treatments and characteristics of soils: while hydrolysis should yield more homogeneous results and isolate oldest fractions. It seems likely that true ages of geologic formations were never obtained from their organic matter and that the oldest organic fraction, contemporaneous with the sediment formation, completely disappears. Thus, most ages from 14 C dating of organic matter of soils must be too recent.
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                Author and article information

                Journal
                applab
                Radiocarbon
                Radiocarbon
                Cambridge University Press (CUP)
                0033-8222
                1945-5755
                1983
                July 18 2016
                : 25
                : 02
                : 409-416
                Article
                10.1017/S0033822200005695
                774d21d8-72cd-422f-92e7-f1a880ff88c2
                © 2016
                History

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